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Seasonality and pollution as keys for interpreting the biodiversity of macroinvertebrates in a Mediterranean stream (Sant Cugat stream, Barcelona)

Abstract:

In October 199.5, the aquatic macroinvertebrate community of the Sant Cugat stream (Barcelona) was examined at various sampling points. Several streams were located inside of the Collserola Metropolitan Park while the main section was in the border area. The community was related to the pollution and the flow seasonality of the stream. Most of the sampling points, located close to the edge of the Park, had permanent flow but with high pollution. On the other hand, inside the Park there were localities with low flow (from <1 l/s to 32 l/s), others with intermittent flow, and several without water: In the fifteen localities sampled a total of 6.5 taxa were found; the highest species richnessfound was 33 taxa of reophilus species (such us simulidae and ephemeroptera) as well as lentic species such as hemiptera, odonata and some coleoptera. Using an ordenation analysis, sampling points were grouped according to theirflow and pollution level. The localities outside the Park (with moderate flow and high pollution) are clustered apart from those inside the Park, where sampling points with permanent water flow and intermittent water flow are clearly differentiated. The differences between the four groups of sampling points with distinct macroinvertebrate community also show differences in the dominance & trophic groups, with collector-gatherers dominant in polluted areas. In temporary streams, the presence of permanent streams (even with very low flow or only pools) is a keyfactor to maintain biodiversity. © Asociación Espaiiola de Limnología.